1. Field of the Invention
The present invention relates generally to the field of sheet metal forming apparatus and, more particularly, to brakes, punches and shears for forming and cutting strips of sheet metal.
2. BACKGROUND DISCUSSION
Various types of sheet metal forming tools and apparatus are known in the art. These tools and apparatus include what are commonly called sheet metal brakes by means of which pieces of sheet metal are rapidly and easily bent along a straight line to form, for example, flanges along edges of the sheet metal pieces. As an alternative to such sheet metal brakes, blocks, usually of wood, and a hammer may be used to manually bend over portions of a piece of sheet metal. However, the use of blocks and a hammer to form a sheet metal bend is slow and usually does not provide a smooth, uniform and straight bend in sheet metal. Moreover, the use of blocks and a hammer to hand-bend sheet metal id slow and requires considerable energy unless the sheet metal is very thin.
Another familiar sheet metal apparatus is a mechanical sheer, constructed somewhat similarly to a guillotine, by means of which sheets or strips of sheet metal are smoothly sheared along a long straight line. Such mechanical shearing apparatus may be manually operated or may, for large sheets of relatively thick sheet metal, be power-operated, and are distinguished from sheet metal hand shears in that the mechanical shearing apparatus are configured for shearing even wide pieces of sheet metal with a single stroke of an elongate cutting blade; whereas, hand-held sheet metal shears make only short cuts with each shearing strike. As a result, hand-held sheet metal shears not only require more effort to cut a wide piece of sheet metal but also provide, even with careful use, an uneven cut with sharp barbs often being formed along the cut between the individual cuts.
Various apparatuses and machines are also known for making holes in sheet metal. Such holes may, of course, be drilled using conventional drill motors and drill bits; however, holes made in this manner often have jagged edges and are out of round. In any event, the drilling of holes in the sheet metal is usually unsatisfactory, since the surrounding regions of the sheet metal may be distorted or torn. The punching of holes is usually more satisfactory for sheet metal, especially thin sheet metal, and is the means most often used. Such hole punches for sheet metal may be constructed to punch either single holds or a plurality of holes at once, and may be manually or power operated.
In some special instances, however, it may be desirable from a production standpoint, to perform braking, punching and shearing operations on strips of sheet metal by means of a single operating stroke. Such braking, punching and shearing of sheet metal strips would be particularly advantageous and time-saving when the production of a large number of similar or identical sheet metal pieces having bends and punched holes is required to be made. Requirements for such similar sheet metal pieces may, for example, be straps for attaching heating and/or air conditioning ducts to building structures.
So far as is known to the present inventor, however, no such combination sheet metal braking, punching and shearing apparatus is available for the production of numbers of straps from, for example, standard coils or rolls of sheet metal. It is, therefore, a principal objective of the present invention to provide such an apparatus.